Field of the Invention
The present disclosure generally relates to the field of medicine, and more particularly, to devices for remote non-contact monitoring of vital signs of a living being, such as motion, breathing and heartbeat, enabling the health status of the organism to be monitored continuously throughout the monitoring time, and to determine its state of wakefulness, sleep, waking from sleep, convulsions, respiratory arrest.
Description of Related Art
Every year devices for remote non-contact monitoring of vital signs of living beings, in particular, human beings, becoming increasingly relevant, as their use in various fields of medicine allows impact on the subject of observation and control to be minimized, and at the same time improving the information content and accuracy of control and diagnostics.
The U.S. patent application Ser. No. 20090203972, IPC A61B 5/00, publ. 13 Aug. 2009 describes an apparatus for remote non-contact monitoring of breathing, heart rate and motion, comprising a processor configured to analyze the signal reflected by a subject without physical contact with the subject, and take measurements of breathing, heart rate and motion of the subject from the reflected signal, and a display configured to provide analyzed and measured parameters to a local or remote user of the apparatus. The apparatus further comprises a sensor coupled to the processor and arranged to receive the signal reflected from the subject. The sensor and processor are both arranged to operate without any direct or indirect physical contact with the subject. The reflected signal is generated by a transmitter collocated with the apparatus. The transmitter is configured to generate a radio-frequency energy signal compatible for use with a living subject. The reflected signal is multiplied with the transmitted signal to output a modulated signal representing a respiration, cardiac and/or motion function.
A disadvantage of the apparatus is the use of the single signal both for transmission and as a reference signal for the multiplier. This either means the use of continuous probing and the reference signal, which automatically leads to a signal reflected from extraneous subjects and interference being received, or limits the distance resolution of the apparatus by the length of the UWB (Ultra Wide Band) signal (i.e., ultra wideband signal) or makes it impossible for the probing signal to comply with the UWB standards that will in all likelihood require a license to use the spectrum band. The U.S. Pat. No. 7,725,150, IPC A61B 5/05 G01S, publ. 25 May 2010, discloses a system for extracting physiological data using an ultra wideband signal comprising a controller connected to the user interface, a first signal processor input, a first analog-to-digital converter input, a first delay range input, and a pulse repetition frequency generator. The first output of the pulse repetition frequency generator is connected to the transmitter input, the output of which is connected to a receiving-transmitting antenna. The second output of the generator is connected to the second input of the delay range, the output of which is connected to the first input of the receiver. The second input of the receiver is connected to the receiving-transmitting antenna, and its output is connected to the second input of the analog-to-digital converter. Output of the analog-to-digital converter is connected to the second input of signal processor, the output of which is connected to the user interface.
A disadvantage of this device is in broadcasting radio frequency pulse signals without radiofrequency content, which makes the device inefficient from an energy point of view.
Prior art reveals systems for monitoring parameters of vital signs of living beings, including non-contact motion, breathing and heart rate sensors (WO2010091168, publ. 12 Aug. 2010, IPC A61B 5/0205, A61B 5/113; WO2010036700, publ. 1 Apr. 2010 IPC G06 F 19/00; WO2008057883, publ. 15 Sep. 2008, IPC A61B 5/00; WO2007143529, publ. 13 Dec. 2007, IPC A41D 27/00 27/02 27/12 27/28 13/00, G21F 3/02). In the above systems, the sensor is a typical radar comprising a continuous or pulsed probing signal generator, a transmitting antenna, a receiving antenna, an amplifier, a mixer and a frequency filter. Disclosed are modifications of radar using short-pulse UWB signals and the Doppler Effect. All these radars, if no original solution is implemented, are limited in resolution, range of the device, as well as of the noise tolerance.
The nearest selected analog (prototype) is a pulsed ultra-wideband sensor (patent of the Russian Federation No. 2369323, IPC A61B 5/08 G01S 13/00, publ. 10 Oct. 2009) for measuring respiratory rate and heart rate. The sensor can be used as a highly sensitive diagnostic tool for the cardiovascular system and respiratory system both under inpatient and outpatient conditions. The sensor comprises a control unit configured to generate a time delay of the synchronization pulse, a probing signal forming circuit, a transmitting and receiving antenna, a probing signal transmitter train, the output of which is connected to the transmitting antenna, a reflected signal receiver circuit, the input of which is connected to the receiving antenna, and a first electronic switch. The input of the first electronic switch is connected to the output of the probing signal forming circuit, and its outputs are connected to the input of the probing signal transmitter circuit and to the reflected signal receiver circuit. The outputs of the channels for processing a reflected signal contained in the reflected signal receiver circuit are connected to a circuit for calculating a respiratory rate and heart rate. The circuit for calculating rates includes two frequency filters, two adders, two signal amplitude calculating units, two signal energy calculating units, two integrators, two comparators, two signal multiplying units, two units for generating a reference signal, second and third electronic switches.
A disadvantage of the device is that the duration of the reference pulse is always equal to the duration of the probing pulse, whereby the reference pulse will always depend on the probing pulse that sets boundaries of the distance sensitivity range in dependence on the occupied bandwidth and resolution of the device, which greatly limits the functionality of the device, reducing the accuracy, reliability and range of the measurements. For instance, to increase the resolution and hence the accuracy of the device, the probing pulse has to be very short, therefore, the reference pulse is very short, and this reduces the operating range of the device. Besides, the construction of the device assumes at least one long UHF communication line (from the first electronic switch either to the probing signal transmitter circuit or to the reflected signal receiver circuit), which, due to rapid attenuation of the UHF signal, limits the maximum allowable distance between the transmitting and receiving antennas in the need for their spacing and imposes additional requirements on PCB material and makes the device relatively expensive.